Road Friendly Suspension Review

A review of the technologies which can be used to test road friendly suspensions is underway, to improve in service testing. The review is being carried out by the Australian Road Research Board (ARRB) in conjunction with the Queensland Department of Transport and Main Roads (TMR).

According to ARRB, the survey of technologies can assist with measuring the performance of road friendly suspension systems or suspension components. Interested parties are asked to provide a description of the technology and any relevant information regarding its functionality.

In order to qualify as a road friendly suspension system it must demonstrate compliance with the following performance characteristics:

static load sharing between axles in a group (no greater than 5 per cent variation between any two axles)

frequency of oscillation of sprung mass (no greater than 2.0 Hz)

damping capability (no less than 20 per cent of critical damping)

damping capability (no greater than 50 per cent of total damping due to friction damping).

These requirements are defined in the Australian Federal regulation Certification of road-friendly suspension systems (Vehicle Standards Bulletin 11) (Department of Transport and Regional Services 2004).

The performance of a suspension system does degrade over time, mainly due to shock absorber wear. In-service compliance refers to a certified Road Friendly Suspension maintaining a satisfactory level of performance while in-service.

To prove in-service compliance the system should perform the following:

Excite: the suspension system under assessment should receive an impulse that is sufficient to excite all relevant modes of oscillation.

Measure: the system must include a method for measuring the response of the suspension system; with sufficient accuracy and resolution.

Analyse: method(s) to analyse the response and determine level of compliance.